gctrpc/order manager: Add ModifyOrder endpoint (#724)

* gctcli: modifyorder stubs

* gctcli: add ModifyOrderRequest and ModifyOrderResponse in rpc.proto

* gctcli: regenerate rpc.pb.go after the addition of ModifyOrder structs

* gctrpc: add ModifyOrder() and regenerate dependent files

* gctcli: modifyorder command now uses newly generated ModifyOrder() RPC

* exchanges/order/orders.go: use time.Time.Equal() instead of ==

* gctrpc: update ModifyOrderRequest and ModifyResponse and regenerate gRPC

* gctcli/commands: rework modifyorder

* engine: implement RPCServer.ModifyOrder

* engine: commit an initial version OrderManager.Modify(), still does not update state of managed orders

* engine: OrderManager.Modify now updates the inner state of managed orders, but introduces race conditions, needs fixes

* engine/order_manager.go: comply with golangci-lint

* gctcli: fix getOrderCommand.ArgsUsage

* gctcli: fix getModifyOrderCommand args and ArgsUsage

* engine: OrderManager.Modify() now correctly updates price of modified order

* engine: RPCServer.ModifyOrder now uses checkParams() as advised

* exchanges: (1) IBotExchange.ModifyOrder now returns a Modify struct, (2) all exchanges are updated to comply with that change

* exchanges/order: Detail.UpdateOrderFromModify also updates the ID

* engine/order_manager: add store.modifyExisting() and use it in OrderManager.Modify to update (on success) the state of the modified order

* exchanges: Bitfinex.ModifyOrder() now returns the ID in case of an error

* engine: OrdetManager.Modify() now emits an order event

* exchanges/bithumb: proper order.payment_currency key

* engine/order_manager: populate more Modify fields as they are needed by (some) exchanges, add comments

* engine: test OrderManager.Modify()

* engine: test store.modifyExisting()

* engine: write a docstring for store.modifyExisting

* engine: OrderManager.Modify() now also sets Modify.Price and Modify.Amount in case of zero values

* engine: TestOrderManager_Modify() now verify the effects of price and/or amount set to 0

* engine: OrderManger.Modify() now uses the commsManager to let observers know of errors

* engine: TestOrderManager_Modify() uses t.Fatal()

* engine: TestOrderManager_Modify() and TestStore_modifyOrder() supply t.Error() with proper messages

* exchanges/order_manager_test: fix a golangci-lint complaint

* engine/order_manager: fix an error comparison bug and simplify

* gctcli/commands: check if either price or amount is set, otherwise we would waste an API call

exchanges/alphapoint/alphapoint_wrapper.go

@@ -263,8 +263,8 @@ func (a *Alphapoint) SubmitOrder(s *order.Submit) (order.SubmitResponse, error)
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (a *Alphapoint) ModifyOrder(_ *order.Modify) (string, error) {
-	return "", common.ErrNotYetImplemented
+func (a *Alphapoint) ModifyOrder(_ *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrNotYetImplemented
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/binance/binance_wrapper.go

@@ -919,8 +919,8 @@ func (b *Binance) SubmitOrder(s *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (b *Binance) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (b *Binance) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/bitfinex/bitfinex_wrapper.go

@@ -647,27 +647,36 @@ func (b *Bitfinex) SubmitOrder(o *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (b *Bitfinex) ModifyOrder(action *order.Modify) (string, error) {
+func (b *Bitfinex) ModifyOrder(action *order.Modify) (order.Modify, error) {
 	if err := action.Validate(); err != nil {
-		return "", err
+		return order.Modify{}, err
 	}
 
 	orderIDInt, err := strconv.ParseInt(action.ID, 10, 64)
 	if err != nil {
-		return action.ID, err
+		return order.Modify{ID: action.ID}, err
 	}
 	if b.Websocket.CanUseAuthenticatedWebsocketForWrapper() {
-		if action.Side == order.Sell && action.Amount > 0 {
-			action.Amount = -1 * action.Amount
-		}
-		err = b.WsModifyOrder(&WsUpdateOrderRequest{
+		request := WsUpdateOrderRequest{
 			OrderID: orderIDInt,
 			Price:   action.Price,
 			Amount:  action.Amount,
-		})
-		return action.ID, err
+		}
+		if action.Side == order.Sell && action.Amount > 0 {
+			request.Amount *= -1
+		}
+		err = b.WsModifyOrder(&request)
+		return order.Modify{
+			Exchange:  action.Exchange,
+			AssetType: action.AssetType,
+			Pair:      action.Pair,
+			ID:        action.ID,
+
+			Price:  action.Price,
+			Amount: action.Amount,
+		}, err
 	}
-	return "", common.ErrNotYetImplemented
+	return order.Modify{}, common.ErrNotYetImplemented
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/bitflyer/bitflyer_wrapper.go

@@ -373,8 +373,8 @@ func (b *Bitflyer) SubmitOrder(s *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (b *Bitflyer) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (b *Bitflyer) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/bithumb/bithumb.go

@@ -314,7 +314,7 @@ func (b *Bithumb) PlaceTrade(orderCurrency, transactionType string, units float6
 
 	params := url.Values{}
 	params.Set("order_currency", strings.ToUpper(orderCurrency))
-	params.Set("Payment_currency", "KRW")
+	params.Set("payment_currency", "KRW")
 	params.Set("type", strings.ToUpper(transactionType))
 	params.Set("units", strconv.FormatFloat(units, 'f', -1, 64))
 	params.Set("price", strconv.FormatInt(price, 10))
@@ -329,7 +329,7 @@ func (b *Bithumb) ModifyTrade(orderID, orderCurrency, transactionType string, un
 
 	params := url.Values{}
 	params.Set("order_currency", strings.ToUpper(orderCurrency))
-	params.Set("Payment_currency", "KRW")
+	params.Set("payment_currency", "KRW")
 	params.Set("type", strings.ToUpper(transactionType))
 	params.Set("units", strconv.FormatFloat(units, 'f', -1, 64))
 	params.Set("price", strconv.FormatInt(price, 10))

exchanges/bithumb/bithumb_wrapper.go

@@ -438,22 +438,31 @@ func (b *Bithumb) SubmitOrder(s *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (b *Bithumb) ModifyOrder(action *order.Modify) (string, error) {
+func (b *Bithumb) ModifyOrder(action *order.Modify) (order.Modify, error) {
 	if err := action.Validate(); err != nil {
-		return "", err
+		return order.Modify{}, err
 	}
 
-	order, err := b.ModifyTrade(action.ID,
+	o, err := b.ModifyTrade(action.ID,
 		action.Pair.Base.String(),
 		action.Side.Lower(),
 		action.Amount,
 		int64(action.Price))
 
 	if err != nil {
-		return "", err
+		return order.Modify{}, err
 	}
 
-	return order.Data[0].ContID, nil
+	return order.Modify{
+		Exchange:  action.Exchange,
+		AssetType: action.AssetType,
+		Pair:      action.Pair,
+		ID:        o.Data[0].ContID,
+
+		Price:  float64(int64(action.Price)),
+		Amount: action.Amount,
+		Side:   action.Side,
+	}, nil
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/bitmex/bitmex_wrapper.go

@@ -575,27 +575,35 @@ func (b *Bitmex) SubmitOrder(s *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (b *Bitmex) ModifyOrder(action *order.Modify) (string, error) {
+func (b *Bitmex) ModifyOrder(action *order.Modify) (order.Modify, error) {
 	if err := action.Validate(); err != nil {
-		return "", err
+		return order.Modify{}, err
 	}
 
 	var params OrderAmendParams
 
 	if math.Mod(action.Amount, 1) != 0 {
-		return "", errors.New("contract amount can not have decimals")
+		return order.Modify{}, errors.New("contract amount can not have decimals")
 	}
 
 	params.OrderID = action.ID
 	params.OrderQty = int32(action.Amount)
 	params.Price = action.Price
 
-	order, err := b.AmendOrder(&params)
+	o, err := b.AmendOrder(&params)
 	if err != nil {
-		return "", err
+		return order.Modify{}, err
 	}
 
-	return order.OrderID, nil
+	return order.Modify{
+		Exchange:  action.Exchange,
+		AssetType: action.AssetType,
+		Pair:      action.Pair,
+		ID:        o.OrderID,
+
+		Price:  action.Price,
+		Amount: float64(params.OrderQty),
+	}, nil
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/bitstamp/bitstamp_wrapper.go

@@ -489,8 +489,8 @@ func (b *Bitstamp) SubmitOrder(s *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (b *Bitstamp) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (b *Bitstamp) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/bittrex/bittrex_wrapper.go

@@ -566,8 +566,8 @@ func (b *Bittrex) SubmitOrder(s *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (b *Bittrex) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (b *Bittrex) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/btcmarkets/btcmarkets_wrapper.go

@@ -530,8 +530,8 @@ func (b *BTCMarkets) SubmitOrder(s *order.Submit) (order.SubmitResponse, error)
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (b *BTCMarkets) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (b *BTCMarkets) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/btse/btse_wrapper.go

@@ -530,8 +530,8 @@ func (b *BTSE) SubmitOrder(s *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (b *BTSE) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (b *BTSE) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/coinbasepro/coinbasepro_wrapper.go

@@ -552,8 +552,8 @@ func (c *CoinbasePro) SubmitOrder(s *order.Submit) (order.SubmitResponse, error)
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (c *CoinbasePro) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (c *CoinbasePro) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/coinbene/coinbene_wrapper.go

@@ -597,8 +597,8 @@ func (c *Coinbene) SubmitOrder(s *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (c *Coinbene) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (c *Coinbene) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/coinut/coinut_wrapper.go

@@ -642,8 +642,8 @@ func (c *COINUT) SubmitOrder(o *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (c *COINUT) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (c *COINUT) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/exmo/exmo_wrapper.go

@@ -467,8 +467,8 @@ func (e *EXMO) SubmitOrder(s *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (e *EXMO) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (e *EXMO) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/ftx/ftx_wrapper.go

@@ -594,9 +594,9 @@ func (f *FTX) SubmitOrder(s *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (f *FTX) ModifyOrder(action *order.Modify) (string, error) {
+func (f *FTX) ModifyOrder(action *order.Modify) (order.Modify, error) {
 	if err := action.Validate(); err != nil {
-		return "", err
+		return order.Modify{}, err
 	}
 
 	if action.TriggerPrice != 0 {
@@ -607,25 +607,42 @@ func (f *FTX) ModifyOrder(action *order.Modify) (string, error) {
 			action.Price,
 			0)
 		if err != nil {
-			return "", err
+			return order.Modify{}, err
 		}
-		return strconv.FormatInt(a.ID, 10), err
+		return order.Modify{
+			Exchange:  action.Exchange,
+			AssetType: action.AssetType,
+			Pair:      action.Pair,
+			ID:        strconv.FormatInt(a.ID, 10),
+
+			Price:        action.Price,
+			Amount:       action.Amount,
+			TriggerPrice: action.TriggerPrice,
+			Type:         action.Type,
+		}, err
 	}
 	var o OrderData
 	var err error
-	switch action.ID {
-	case "":
+	if action.ID == "" {
 		o, err = f.ModifyOrderByClientID(action.ClientOrderID, action.ClientOrderID, action.Price, action.Amount)
 		if err != nil {
-			return "", err
+			return order.Modify{}, err
 		}
-	default:
+	} else {
 		o, err = f.ModifyPlacedOrder(action.ID, action.ClientOrderID, action.Price, action.Amount)
 		if err != nil {
-			return "", err
+			return order.Modify{}, err
 		}
 	}
-	return strconv.FormatInt(o.ID, 10), err
+	return order.Modify{
+		Exchange:  action.Exchange,
+		AssetType: action.AssetType,
+		Pair:      action.Pair,
+		ID:        strconv.FormatInt(o.ID, 10),
+
+		Price:  action.Price,
+		Amount: action.Amount,
+	}, err
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/gateio/gateio_wrapper.go

@@ -518,8 +518,8 @@ func (g *Gateio) SubmitOrder(s *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (g *Gateio) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (g *Gateio) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/gemini/gemini_wrapper.go

@@ -551,8 +551,8 @@ func (g *Gemini) SubmitOrder(s *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (g *Gemini) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (g *Gemini) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/hitbtc/hitbtc_wrapper.go

@@ -575,8 +575,8 @@ func (h *HitBTC) SubmitOrder(o *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (h *HitBTC) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (h *HitBTC) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/huobi/huobi_wrapper.go

@@ -898,8 +898,8 @@ func (h *HUOBI) SubmitOrder(s *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (h *HUOBI) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (h *HUOBI) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/interfaces.go

@@ -51,7 +51,7 @@ type IBotExchange interface {
 	SupportsWithdrawPermissions(permissions uint32) bool
 	GetFundingHistory() ([]FundHistory, error)
 	SubmitOrder(s *order.Submit) (order.SubmitResponse, error)
-	ModifyOrder(action *order.Modify) (string, error)
+	ModifyOrder(action *order.Modify) (order.Modify, error)
 	CancelOrder(o *order.Cancel) error
 	CancelBatchOrders(o []order.Cancel) (order.CancelBatchResponse, error)
 	CancelAllOrders(orders *order.Cancel) (order.CancelAllResponse, error)

exchanges/itbit/itbit_wrapper.go

@@ -416,8 +416,8 @@ func (i *ItBit) SubmitOrder(s *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (i *ItBit) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (i *ItBit) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/kraken/kraken_wrapper.go

@@ -755,8 +755,8 @@ func (k *Kraken) SubmitOrder(s *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (k *Kraken) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (k *Kraken) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/lbank/lbank_wrapper.go

@@ -456,8 +456,8 @@ func (l *Lbank) SubmitOrder(s *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (l *Lbank) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (l *Lbank) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/localbitcoins/localbitcoins_wrapper.go

@@ -414,8 +414,8 @@ func (l *LocalBitcoins) SubmitOrder(s *order.Submit) (order.SubmitResponse, erro
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (l *LocalBitcoins) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (l *LocalBitcoins) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/okgroup/okgroup_wrapper.go

@@ -312,8 +312,8 @@ func (o *OKGroup) SubmitOrder(s *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (o *OKGroup) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (o *OKGroup) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/order/orders.go

@@ -196,7 +196,7 @@ func (d *Detail) UpdateOrderFromDetail(m *Detail) {
 		updated = true
 	}
 	if updated {
-		if d.LastUpdated == m.LastUpdated {
+		if d.LastUpdated.Equal(m.LastUpdated) {
 			d.LastUpdated = time.Now()
 		} else {
 			d.LastUpdated = m.LastUpdated
@@ -214,6 +214,10 @@ func (d *Detail) UpdateOrderFromDetail(m *Detail) {
 // by comparing passed in and existing values
 func (d *Detail) UpdateOrderFromModify(m *Modify) {
 	var updated bool
+	if m.ID != "" && d.ID != m.ID {
+		d.ID = m.ID
+		updated = true
+	}
 	if d.ImmediateOrCancel != m.ImmediateOrCancel {
 		d.ImmediateOrCancel = m.ImmediateOrCancel
 		updated = true
@@ -351,7 +355,7 @@ func (d *Detail) UpdateOrderFromModify(m *Modify) {
 		updated = true
 	}
 	if updated {
-		if d.LastUpdated == m.LastUpdated {
+		if d.LastUpdated.Equal(m.LastUpdated) {
 			d.LastUpdated = time.Now()
 		} else {
 			d.LastUpdated = m.LastUpdated

exchanges/poloniex/poloniex_wrapper.go

@@ -541,14 +541,14 @@ func (p *Poloniex) SubmitOrder(s *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (p *Poloniex) ModifyOrder(action *order.Modify) (string, error) {
+func (p *Poloniex) ModifyOrder(action *order.Modify) (order.Modify, error) {
 	if err := action.Validate(); err != nil {
-		return "", err
+		return order.Modify{}, err
 	}
 
 	oID, err := strconv.ParseInt(action.ID, 10, 64)
 	if err != nil {
-		return "", err
+		return order.Modify{}, err
 	}
 
 	resp, err := p.MoveOrder(oID,
@@ -557,10 +557,20 @@ func (p *Poloniex) ModifyOrder(action *order.Modify) (string, error) {
 		action.PostOnly,
 		action.ImmediateOrCancel)
 	if err != nil {
-		return "", err
+		return order.Modify{}, err
 	}
 
-	return strconv.FormatInt(resp.OrderNumber, 10), nil
+	return order.Modify{
+		Exchange:  action.Exchange,
+		AssetType: action.AssetType,
+		Pair:      action.Pair,
+		ID:        strconv.FormatInt(resp.OrderNumber, 10),
+
+		Price:             action.Price,
+		Amount:            action.Amount,
+		PostOnly:          action.PostOnly,
+		ImmediateOrCancel: action.ImmediateOrCancel,
+	}, nil
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/yobit/yobit_wrapper.go

@@ -413,8 +413,8 @@ func (y *Yobit) SubmitOrder(s *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (y *Yobit) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (y *Yobit) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number

exchanges/zb/zb_wrapper.go

@@ -511,8 +511,8 @@ func (z *ZB) SubmitOrder(o *order.Submit) (order.SubmitResponse, error) {
 
 // ModifyOrder will allow of changing orderbook placement and limit to
 // market conversion
-func (z *ZB) ModifyOrder(action *order.Modify) (string, error) {
-	return "", common.ErrFunctionNotSupported
+func (z *ZB) ModifyOrder(action *order.Modify) (order.Modify, error) {
+	return order.Modify{}, common.ErrFunctionNotSupported
 }
 
 // CancelOrder cancels an order by its corresponding ID number